1. Field of the Invention
The present invention relates to a light emitting device and a method of manufacturing the same.
2. Description of the Related Art
A light emitting diode (LED) according to the related art, for example, one disclosed in Japanese Utility Model No. 3068914 has a light emitting layer having a stack structure in which, for example, an under layer 10B formed based on an MOCVD method, a first compound semiconductor layer 11 of a first conduction type (e.g., n-type), an active layer 12, and a second compound semiconductor layer 13 of a second conduction type (e.g., p-type) are stacked over a substrate 10A including, for example, sapphire, as shown in a schematic sectional view in FIG. 8. A second electrode 14 is provided over the second compound semiconductor layer 13. In addition, a part of the first compound semiconductor layer 11 is exposed by removing a part of the second compound semiconductor layer 13 and a part of the active layer 12, and a first electrode 15 is provided over the exposed part of the first compound semiconductor layer 11. A current is passed from the second electrode 14 through the part of the active layer 12 beneath the second compound semiconductor layer 13 thus left to the first compound semiconductor layer 11 and the first electrode 15. As a result, in the active layer 12, a quantum well structure of the active layer 12 is excited by the injection of the current, and a light emitting state is obtained over the whole surface area.
In a light emitting diode of the substrate-side light pickup type, the light emitted from the active layer 12 is transmitted directly through the substrate 10A to go out to the exterior, or is reflected by the second electrode 14 to be transmitted through the substrate 10A and to go out to the exterior. On the other hand, in a light emitting diode of the electrode transmitted light pickup type, the light emitted from the active layer 12 is transmitted through the second electrode 14 to go out to the exterior. Therefore, not only the reliability of the compound semiconductor layer serving as the light emitting layer but also the reliability (e.g., environmental resistance and uniformity) of the electrodes are of extreme importance.
As a material constituting the second electrode 14, silver (Ag) having a high reflectance is used in the light emitting diode of the substrate-side light pickup type, whereas ITO for constituting a transparent electrode is used in the light emitting diode of the electrode transmitted light pickup type. In order to enhance the reliability of the second electrode 14, usually, the second electrode 14 is covered with an insulating film 116 formed by a CVD method such as plasma CVD, etc. or a PVD method such as vacuum evaporation, sputtering, etc. Openings 18A and 18B are provided in those parts of the insulating film 16 which are located on the upper side of the first electrode 15 and the second electrode 14, and a first contact part 19A and a second contact part 19B are provided respectively over the exposed parts of the first electrode 15 and the second electrode 14.